[IPV6]: Handle ECN correctly in ip6ip6 tunnels.

This patch adds ECN encapsulation/decapsulation to ip6_tunnel.c.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_tunnel.c

@@ -48,6 +48,8 @@
 #include <net/addrconf.h>
 #include <net/ip6_tunnel.h>
 #include <net/xfrm.h>
+#include <net/dsfield.h>
+#include <net/inet_ecn.h>
 
 MODULE_AUTHOR("Ville Nuorvala");
 MODULE_DESCRIPTION("IPv6-in-IPv6 tunnel");
@@ -490,6 +492,15 @@ ip6ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	read_unlock(&ip6ip6_lock);
 }
 
+static inline void ip6ip6_ecn_decapsulate(struct ipv6hdr *outer_iph,
+					  struct sk_buff *skb)
+{
+	struct ipv6hdr *inner_iph = skb->nh.ipv6h;
+
+	if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
+		IP6_ECN_set_ce(inner_iph);
+}
+
 /**
  * ip6ip6_rcv - decapsulate IPv6 packet and retransmit it locally
  *   @skb: received socket buffer
@@ -531,6 +542,7 @@ ip6ip6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
 		skb->dev = t->dev;
 		dst_release(skb->dst);
 		skb->dst = NULL;
+		ip6ip6_ecn_decapsulate(ipv6h, skb);
 		t->stat.rx_packets++;
 		t->stat.rx_bytes += skb->len;
 		netif_rx(skb);
@@ -621,6 +633,7 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	u8 proto;
 	int err;
 	int pkt_len;
+	int dsfield;
 
 	if (t->recursion++) {
 		stats->collisions++;
@@ -646,6 +659,7 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	memcpy(&fl, &t->fl, sizeof (fl));
 	proto = fl.proto;
 
+	dsfield = ipv6_get_dsfield(ipv6h);
 	if ((t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS))
 		fl.fl6_flowlabel |= (*(__u32 *) ipv6h & IPV6_TCLASS_MASK);
 	if ((t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL))
@@ -717,6 +731,8 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 	skb->nh.raw = skb_push(skb, sizeof(struct ipv6hdr));
 	ipv6h = skb->nh.ipv6h;
 	*(u32*)ipv6h = fl.fl6_flowlabel | htonl(0x60000000);
+	dsfield = INET_ECN_encapsulate(0, dsfield);
+	ipv6_change_dsfield(ipv6h, ~INET_ECN_MASK, dsfield);
 	ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	ipv6h->hop_limit = t->parms.hop_limit;
 	ipv6h->nexthdr = proto;